The association between birth weight and anxiety disorders in young adults.

Recent evidence has linked birth weight to later behaviour/mental disorders, yet studies have hitherto neglected to investigate the relationship between birth weight and adult anxiety disorders. Prospectively collected data from 2210 mother/offspring pairs of the Mater University Study of Pregnancy (MUSP) birth cohort was used to test for associations between birth weight z-score and four major groupings of DSM-IV anxiety disorders. Birth weight z-score was linearly and inversely associated with lifetime diagnosis of post-traumatic stress disorders at 21 years, with those falling within the smallest birth weight quintile group at almost two-fold increased odds (OR=1.96, 95% CI: 1.10, 3.52) of being diagnosed with the disorder compared to those falling within the largest group. The association remained when subsequent analysis restricted the sample to those exposed to trauma. This is the first study in which birth weight has been found to be associated with post-traumatic stress disorders in adults.